1. Field of the Invention
This invention relates to a magnetostrictive resonator whose presence can be detected by a magnetostrictive resonator detection apparatus based on a magnetostriction phenomenon, a road in which the magnetostrictive resonator is buried, and a method of burying the magnetostrictive resonator.
2. Description of the Related Art
In recent years, application of magnetostrictive resonators has widened in such a manner that magnetostrictive resonators are buried in a road for detecting a vehicle on the road or that a magnetostrictive resonator is attached to a commodity product: in a store for finding the commodity product not yet paid for and illegally taken out at the exit of the store.
A phenomenon in which dimension change called xe2x80x9cJoule effectxe2x80x9d is caused by applying ani external magnetic field to ferrite, amorphous material of ferromagnetic material, etc., is referred to as a magnetostriction phenomenon. If an AC magnetic field is applied to a magnetostrictive member having such nature by a calling electromagnetic wave while a bias magnetic field like a direct current is applied to the magnetostrictive member, when the AC magnetic field gives magnetostrictive displacement to magnetostrictive resonator and the frequency of the AC magnetic field matches the resonance frequency of the magnetostrictive member, the maximum magnetostrictive displacement can be given to the magnetostrictive resonator. If the AC magnetic field caused by the calling electromagnetic wave is stopped, mechanical resonance of the magnetostrictive resonator causes an electromagnetic wave to be generated only for a short time, thus the electromagnetic wave can be detected for detecting the presence of the magnetostrictive resonator.
The detection method will be simply discussed. As shown in FIG. 9, a rectangular magnetostrictive member 31 is made of a thin plate provided by extending a ferromagnetic substance of amorphous material, etc., and a magnetized magnetic member 32 like a tape belt, for example, is placed near the magnetostrictive member 31. In this state, a calling electromagnetic wave is projected from the arrow X direction for AC excitation. When the frequency is changed and matches the resonance frequency of the magnetostrictive member 31, the magnetostrictive member 31 vibrates in the length direction thereof. FIG. 10 shows the magnetization displacement characteristic. If the magnetic member 32 does not exist, vibration of displacement width Mo is produced for AC excitation Ho; if magnetic bias Hd caused by the magnetic member 32 is applied, vibration of displacement width MA can be produced for AC excitation HA caused by the calling electromagnetic wave. If the calling electromagnetic wave is stopped, mechanical resonance of the magnetostrictive member 31 continues for a short time and the magnetostrictive member 31 is generated by a villery effect in which the magnetization state changes in response to deformation of the magnetostrictive member 31 because of a mechanical stress caused by the mechanical resonance, thus the electromagnetic wave can be detected for knowing the presence of the magnetostrictive member. If a number of magnetostrictive members different in resonance frequency are combined and placed, a combination of the resonance frequencies is detected, whereby specific information indicated by the position can also be known.
FIG. 11 shows a conventional magnetostrictive resonator example. The magnetostrictive resonator comprises two magnetostrictive members 41a and 41b like extended thin plates placed in a frame 42 and brought close to a magnetic material 43 of a ferromagnetic substance magnetized. The magnetostrictive members 41a and 41b differ in length and resonate with different resonance frequencies, thus can cover different calling frequencies.
Since the conventional magnetostrictive resonator as shown in FIG. 11 comprises a number of magnetostrictive members housed in the frame 42, the magnetostrictive members 41a and 41b may come in contact with each other depending on the attitude, causing the vibration mode to change or the frequency to shift as hindrance. It is also feared that play in the shorter magnetostrictive member 41b may occur in the frame 42 and the magnetostrictive member 41b may move in the frame, so that the magnetostrictive member goes away from a detection antenna.
It is therefore an object of the invention to provide a small and compact magnetostrictive resonator that can comprise various magnetostrictive members in combination, a road in which the magnetostrictive resonator is buried, and a method of burying the magnetostrictive resonator.
To the end, according to a first aspect of the invention, there is provided a magnetostrictive resonator comprising a belt-like magnetic member for holding a magnetic bias, a first magnetostrictive member placed facing one side of the magnetic member, a second magnetostrictive member placed facing the opposite side of the magnetic member, a first storage body provided with a storage section for storing the first magnetostrictive member, and a second storage body provided with a storage section for storing the second magnetostrictive member, so that the magnetostrictive resonator having two magnetostrictive members placed on both sides of the magnetic member can be formed small and compact.
In a second aspect of the invention, in the magnetostrictive resonator according to a first aspect of the invention, the first and second magnetostrictive members differ in length, so that the magnetostrictive resonator having two different resonance frequencies can be formed small and compact.
In a third aspect of the invention, in the magnetostrictive resonator according to a second aspect of the invention, one end in the length direction of the first magnetostrictive member and one end in the length direction of the second magnetostrictive member are at symmetrical positions with each other with the belt-like magnetic member between, so that the magnetostrictive resonator having two different resonance frequencies can be formed small and compact and the radio wave emitted from the magnetostrictive member can be detected with high sensitivity at an antenna disposed on such one end.
In a fourth aspect of the invention, in the magnetostrictive resonator according to the second or third aspect of the invention, the storage sections of the first and second storage bodies differ in dimensions matching the dimensions of the first and second magnetostrictive members stored in the first and second storage bodies, so that play in the magnetostrictive member in the storage section can be eliminated.
In a fifth aspect of the invention, in a first aspect of the magnetostrictive resonator, the belt-like magnetic member is magnetized on both sides as different patterns, so that if the size of the magnetostrictive member or the storage section in the frame is not changed, the resonance frequency can be changed only by changing the magnetization method and the types of parts can be lessened.
According to a sixth aspect of the invention, there is provided a magnetostrictive resonator comprising a belt-like magnetic member for holding a magnetic bias, a plurality of magnetostrictive members facing one side of the magnetic member and being aligned in the length direction, and a storage body provided with a storage section for separately storing the magnetostrictive members. According to a seventh aspect of the invention, there is provided a magnetostrictive resonator comprising a belt-like magnetic member for holding a magnetic bias, a plurality of magnetostrictive members facing one side of the belt-like magnetic member and being placed so that the long sides of the magnetostrictive members are aligned, and a storage body provided with a storage section for separately storing the magnetostrictive members. Thus, the magnetostrictive resonator having a plurality of magnetostrictive members can be formed small and compact.
According to an eighth aspect of the invention, there is provided a magnetostrictive resonator comprising a belt-like magnetic member for holding a magnetic bias, a plurality of magnetostrictive members facing one side of the magnetic member and being aligned in the length direction and a lateral direction, and a storage body provided with a storage section for separately storing the magnetostrictive members. The storage body has a structure as provided by combining the sixth and seventh aspects of the invention, and the magnetostrictive resonator having more magnetostrictive members can be formed small and compact.
In a ninth aspect of the invention, the magnetostrictive resonator as claimed in any of the sixth to eighth aspects of the invention further includes a storage body provided with a storage section facing the opposite side of the belt-like magnetic member for separately storing a plurality of magnetostrictive members. The magnetostrictive resonator having a large number of magnetostrictive members on both sides of the belt-like magnetic member can be formed small and compact.
In a tenth aspect of the invention, in the magnetostrictive resonator as claimed in any of the sixth to ninth aspects of the invention, the magnetostrictive members differ in length, so that the magnetostrictive resonator having different resonance frequencies can be formed small and compact.
In an eleventh aspect of the invention, in a tenth aspect of the magnetostrictive resonator, the storage section of the storage body differ in dimensions matching dimensions of the magnetostrictive members stored in the storage body, so that play in the magnetostrictive member in the storage section can be eliminated.
In a twelfth aspect of the invention, in the sixth, eighth or ninth aspects of the invention, the magnetostrictive resonator as defined in the sixth, eighth or ninth aspect, the magnetostrictive members differ in length and are arranged in the length order in the length direction. The longer the magnetostrictive member, the stronger an electromagnetic wave emitted. Thus, the magnetostrictive resonator having different resonance frequencies can be formed small and compact and radio waves emitted from all magnetostrictive members can be detected with high sensitivity at an antenna disposed on the side of the shorter magnetostrictive member.
In a thirteenth aspect of the invention, in the magnetostrictive resonator as claimed in any of the seventh to tenth aspects of the invention, one end in the length direction of one magnetostrictive member is adjacent to one end in the length direction of another magnetostrictive member, so that the magnetostrictive resonator having different resonance frequencies can be formed small and compact and radio waves emitted from the magnetostrictive members can be detected with high sensitivity at an antenna disposed on such one end.
In a fourteenth aspect of the invention, in the magnetostrictive resonator as claimed in any of the sixth to ninth aspects of the invention, the belt-like magnetic member comprises different magnetization patterns corresponding to the magnetostrictive members. Thus, the resonance frequency can be changed simply by changing the magnetization method without changing the size of the magnetostrictive member or the storage section in the frame, and the types of parts can be decreased.
In a fifteenth aspect of the invention, in the magnetostrictive resonator as defined in the seventh aspect of the invention, the magnetostrictive members are spaced a predetermined distance apart and the length of the belt-like magnetic member in the same direction as the lateral direction of the magnetostrictive member, namely, the short side direction thereof is longer than the length in the same direction as the length direction of the magnetostrictive member. The magnetostrictive resonator can be detected with high sensitivity if the antenna of a magnetostrictive resonator detection apparatus is moved at high speed in the arrangement direction of the magnetostrictive members of the magnetostrictive resonator.
According to a sixteenth aspect of the invention, there is provided a road wherein if a magnetostrictive resonator as defined in the third aspect of the invention is used, the side where one end in the length direction of the first magnetostrictive member and one end in the length direction of the second magnetostrictive member are at symmetrical positions with each other with the belt-like magnetic member between is buried closer to a road face than the opposite end, and wherein if a magnetostrictive resonator according to the thirteenth aspect of the invention is used, the side where one end in the length direction of one magnetostrictive member is adjacent to one end in the length direction of another magnetostrictive member is buried closer to a road face than the opposite end. Since the magnetostrictive members are placed on the side close to the road surface, a radio wave emitted from each magnetostrictive member can be detected with high sensitivity at an antenna installed on a vehicle.
According to a seventh aspect of the invention, there is provided a road wherein a magnetostrictive resonator as defined in the twelfth aspect of the invention is buried with a longer magnetostrictive member away from a road face. Since the longer magnetostrictive member emits a stronger electromagnetic wave, radio waves emitted from all magnetostrictive members can be detected with high sensitivity at an antenna installed on a vehicle.
According to an eighteenth aspect of the invention, there is provided a road wherein a magnetostrictive resonator as defined in the fifteenth aspect of the invention is buried so that a plurality of magnetostrictive members are aligned in the vehicle travel direction. Thus, high-sensitivity detection is enabled if the antenna of a magnetostrictive resonator detection apparatus is moved at high speed in the arrangement direction of the magnetostrictive members of the magnetostrictive resonator.
According to a ninteenth aspect of the invention, there is provided a magnetostrictive resonator burying method, if a magnetostrictive resonator as defined in the third aspect of the invention is used, comprising the step of burying the magnetostrictive resonator so that the side where one end in the length direction of the first magnetostrictive member and one end in the length direction of the second magnetostrictive member are at symmetrical positions with each other with the belt-like magnetic member between becomes closer to the buried face than the opposite end, if a magnetostrictive resonator as defined in the thirteenth aspect of the invention is used, comprising the step of burying the magnetostrictive resonator so that the side where one end in the length direction of one magnetostrictive member is adjacent to one end in-the length direction of another magnetostrictive member-becomes closer to the buried face than the opposite end. Since the magnetostrictive members are placed on the side close to the buried face, a radio wave emitted from each magnetostrictive member can be detected with high sensitivity at a detection antenna.
According to a twentieth aspect of the invention, there is provided a magnetostrictive resonator burying method comprising the step of burying a magnetostrictive resonator as defined in the twelfth aspect of the invention so that a longer magnetostrictive member is away from the buried face. Since the longer magnetostrictive member emits a stronger electromagnetic wave, radio waves emitted from all magnetostrictive members can be detected with high sensitivity at an antenna installed on a vehicle.
According to a 21-st aspect of the invention, there is provided a magnetostrictive resonator burying method comprising the step of burying a magnetostrictive resonator as defined in the fifteenth aspect of the invention so that a plurality of magnetostrictive members are aligned in the vehicle travel direction. Thus, high-sensitivity detection is enabled if the antenna of a magnetostrictive resonator detection apparatus is moved at high speed in the arrangement direction of the magnetostrictive members of the magnetostrictive resonator.